Process of galvanizing sheet metal



s p 1930. B. P. FINKBONE 1,776,352

PROCESS OF GALVANIZING SHEET IETAL Filed Nov. 30, 1925 f INVENTOR.

MWJMM A TTORNEYG Patented Sept. 30, 1930 NITED STATES PATENT OFFICE BENJAMIN P. FINKBONE, OF MIDDLE'I'OWN, OHIO, ASSIGNOR TO THE AMERICAN ROLL- ING- MILL COMPANY, OF IIIDDLETOWN, OHIO, A CORPORATION 01 OHIO rnocass on onnvamzmo SHEET METAL Application filed November 30, 1925. Serial No. 72,138.

My invention relates to the problem of coating a piece of sheet metal with commercially pure zinc coating. So far as I am aware no one in the past has accomplished this, and I find that a thicker coating of pure zinc can be imposed upon the surface of a piece of sheet metal than is practical 1n the instance ofthe usual impure spelters 1n general use today, because the pure zinc appears to be more tightly adherent, and more ductlle so as to permit the sheet to be worked up, corrugated or formed without loosening or cracking the coating. By pure zinc or commercially pure zinc I refer to either electrolytic zinc or to commercially available zinc that is insufliciently alloyed to be distinct therefrom in its properties.

I have found that the necessary temperatures employed in maintaining a bath of pure zinc in proper molten condition, in order to properly coat a piece of sheet metal, are sufliciently higher than those called for 1n theusual galvanizing processes, to requlre a difierent mode of procedure.

In the first place the flux must be of a particular type, which, although known in the arts, has not been advanced for use under hi htemperatures so far as I am advised.

n the next place the highly heated flux and the zinc in the presence of the iron body of a flux box, results in so much zinc and iron alloy, that the same renders the process impossible, due to this alloy or dross collecting on the surface of the zinc and spot- I ting the sheet, and this has to be avoided by lining the flux box with a material which will not react with the metal or the flux.

In the third place, I have found it desirable to control the temperature in the flux box which will serve to maintain a proper flux bath at the zinc temperatures called for when using pure zinc, with'some mode of applying heat in addition to those ordinarily employed.

Finally in removing the sheet from the zinc pot, after it has passed down through the flux box, and is then to be drawn out through the exit rolls, I find it necessary to provide a particular mode of preventing the rolls The usual mode of cleaning the exit rolls with a body of flux, will not serve for the reasonvthat the high temperatures called for, make the cleansing flux or sal-ammoniac so liquid that it will carry around on the rolls. This as has been stated, spots the sheets. By using a body of some inert substance such as sand, to wipe the exit rolls, and a particularly moist sal-ammoniac imposed on the top of the sand so as to contact with the rolls, I provide for clean rolls, and still keep the rolls in proper condition of' coating with molten zinc.

While I have devised preferred mechanism for accomplishing the various steps of my process, still inherently it is a novel process of treating a piece of sheet metal and in this application I propose to state the steps of treatment as independent of mechanism.

I have illustrated in the drawing a preferred mechanism for accomplishing my purpose, in which:

The figure is a central longitudinal section of an apparatus for carrying out my invention.

The equipment for use with my novel galvanizing process follows the usual lines of construction in sheet metal galvanizing except for several details of structure. Thus I have shown the kettle 1, set in suitable brickwork 2. Arranged to be driven within the kettle are the bottom rolls 3, and extending from the receiving end of the kettle to the bottom rolls and from thence to the exit rolls 4, are the curved guides 4, which define the path of movement of a piece of sheet metal, same being inserted into the guides, fed along by the bottom rolls, and finally grasped by the exit rolls and fed out of the kettle.

The kettle is heated by suitable burners 5, in the instance shown being gas burners arranged around the kettle. A hollow rectangular casing 6 formed of metal lined with fire clay or fire bricks is suitably supported at the receiving end of the kettle, and in connection with whatever type of cover is used for the kettle, there will be provided a baflle bar 7 located close to the exit rolls 4 on the side toward the body of the kettle.

from carrying flux in spots onto the sheets. The C ing 6 is the 11 and as has been noted, in m process, the box must be lined with material highl resistant to heat and chemical action. A so I have provided the flux box with a hollow outer wall leaving space 8 in which is set a gas burner 9.

' In use the kettle is filled with molten zinc, in my process the commercially pure zinc being used instead of an'alloy as is customary in galvanizing sheet metal. The zinc is kept the required purpose of providing the proper surface cleaning'under the particular conditions as to nature of molten metal. and required temperatures involved.

To state the exact proportions of these two substances would possibl mislead more than assist those skilled in t e art, because the amount of cleaning required on the sheet metal is dependent upon how effective has been the prior pickling or other cleansing action. I use a flux formed of 60% ammonium.

chloride and 40% zinc ammonium chloride, which I find gives the best results, but increase of the amount of ammonium chloride might be required forunclean sheets. Naturally zinc ammonium chloride will develop in the flux after its use has been started and this should be taken into account.

The theory of flux action is more or' less a matter of speculation, and in practice the requirements are the prevention of flux adhering to the sheet, proper cleanin action, 1 and minimum loss of spe ter, throug chemical action.

In order to rovide the high heat necessary I for the flux, use the additional burner in the flux box wall, orv insert a special double .walled box into the flux box for roviding the additional gas flame, or equiva ent source of heat.

At the exit rolls I provide a suflicient amount ofsand of high grade (ordinarily riversand will not serve), which is floated on the zinc between the inner exit roll and the baflle bar, and the outer exit roll and the kettle wall as indicated at 11. On top of the sand I place ammonium chloride (sal ammoniac) as at 12, which I kee wet with proper spraying, withwater. 's arrangement at the exit end of the kettle keeps the exit rolls well plated. with molten zinc, and still keeps them clean by the action of the flux followed by the scrubbing action of the sand, which is in moist condition also. duetothe moisture of-the flux. Y

As a process, my invention could be well used with other equipment, the requirements being the proper treatment for the exit rolls, and the properly fluxed entrance of the sheets into the bath, with the added heat used, and

the special flux protected by materials which will not react chemically at the high temperatures, causing a dross on the zinc surface.

This mode of procedure is to be contrasted with the usual one in galvanizing sheets in which the flux on the exit rolls merely floats there and is not so liquid as to be carried around with them. Y

A sheet of material coated with zinc using the mode of procedure outlined, has been found to have a smoother and denser coat and one more adherent to the metal. The chance of deterioration by corrosion and abrasion is ounce coating may be app ied to a like unit of area, andthe working properties willbe just as good. The custom of the trade calculating zinc coatin is as follows :As an instance, a sheet 2 eet wide by 2 feet long. would be considered as having four square feet, and a two ounce coating would consist of eight ounces of zinc on the above dimensioned sheet. It is a physical fact that there are eight square feet of surface of the instanced sheet, but the custom of the trade with reference to coatings is to designate it as having four square feet.

y thickness of coating I provide for longer life and less chance of destruction by abra sion and the like, and by pureness of coating I cut down the chances of loss by normal processes of corrosion to which galvanized v metal is subjected.

What I-claim as my invention,'is v 1. In a rocess of-galvanizing sheet metal,

wherein t e sheet metal is drawn by rolls through a bath the steps which consist in using as a bath molten zinc substantially free of impurities, or alloying. elements, and keeping said rolls clean by a body of inert abrasive substance in finely divided form, such as sand,.on the top of which is supported a body of moistened flux through which the rolls wipe.

2. In. a rocess of galvanizing sheet metal, wherein t e sheet metal is drawn by rolls through a bath, the steps which consist in using as a bath molten zinc substantially free of impurities or alloying elements, floating a body of flux on the zinc where the sheet enters the. same, protecting the flux by an inert surrounding body to revent forma- .tion of dross, and keepingvsald rolls clean by a body of inert abrasive substance in finely divided form, such as sand, on the top of which is supported a body of moistened flux through wh1ch the rolls wipe.

3. In a process of galvanizing sheet metal,

.wherein the sheet metal is drawn into a bath,

the steps which consist in using as a bath molten zinc substantially free of impurities or alloying elements, floating a body of flux on the zinc where the sheet enters the same, said flux containing zinc ammonium chloride, protecting the flux by an inert surrounding body to prevent formation of dross, applying heat to the zinc to maintain it in molten condition, and keeping said rolls clean by a body of inert, abrasive substance in finely divided form, such as sand, on the top of which is supported a body of moistened flux through 'which the rolls Wipe.

BENJAMIN P. FINKBONE. 

